They also challenged statements by the secretary of the Guardian Council, Ahmad Jannati, who told worshippers during Friday prayers in Tehran that a meeting between the president, speaker and Guardian Council resulted in good understanding.

During that sermon, Mr. Jannati pledged to reverse any possible mistakes the Guardian Council might have made when disqualifying thousands of mostly reformist candidates from running in Iran's February 20 elections.

But Mr. Jannati also said the president and parliament speaker, who met with the Guardian Council last week to contest the massive election bans, realized after their meeting that they had been given wrong information.

In their statement, President Khatami and Mr. Karroubi demanded the details of their meeting with the Guardian Council be made public so that Iranian voters could make their own decisions as to why the Guardian Council chose to ban the candidates.

The Guardian Council is an unelected, conservative watchdog group of 12 Islamic clerics and lawyers who can screen potential candidates and veto legislation that does not conform to Islamic principles.

In addition to barring thousands of candidates, the council also disqualified more than 80 current members of parliament, but it did not publicly provide reasons why.

That decision has prompted many parliament members to hold an ongoing sit-in protest in parliament. Dozens of top government officials have threatened to resign if the large-scale disqualification of candidates goes through.

Iran's supreme leader, Ayatollah Ali Khamenei, intervened in the political standoff last week and ordered the Guardian Council to complete a thorough review of its decision.

The council has reinstated more than 200 of the previously disqualified candidates so far and has pledged to complete its review by January 30.